1. Field of the Invention
This disclosure relates to a method for manufacturing a switchable display.
2. Description of the Related Art
The electrophoretic display (EPD) is a non-emissive device based on an electrophoresis phenomenon influencing charged particles suspended in a liquid solvent or a gaseous medium. An EPD typically comprises a pair of opposing, spaced-apart and plate-like electrodes, with ribs pre-determined at a certain distance between the electrodes. A suspension composed of suspended charged display particles and a dielectric medium is enclosed between the two plates. At least one of the electrodes is transparent such that the state of the charged display particles can be viewed through the transparent electrode. Recently the EPD technology has been improved, wherein the EPD is formed from a plurality of microcups which are formed integrally with one another as portions of a structured two-dimensional array assembly. Each microcup of the array assembly is filled with a suspension or a dispersion of charged display particles in a liquid solvent or a gaseous medium, and then sealed to form an electrophoretic cell. When a voltage difference is imposed between the two electrodes, the charged display particles migrate by attraction to the plate which has opposite polarity to that of the charged display particles. Thus, the changes in the color or shadings display an image through the transparent electrode by selectively charging the microcups of the array assembly on the plates.
The EPD can be a powder type display in which charged display particles of different polarities and contrast colors are suspended in a gaseous medium in the microcups of the array assembly. The powder-type EPD may have advantages of a very fast responsiveness and a broader range of viewing angles than comparable reflection-type LCDs, and may comparatively use less electricity. Moreover, the powder-type EPD may have a very small thickness such that it can solve the problem of image distortion when the display is bent.
FIG. 1A shows a method to fill charged display particles into cells of microcups. The charged display particles are filled into the cells by: setting a substrate 102, on which the cells 104 are formed by means of ribs 106, and scattering the charged display particles 108 from a nozzle 110 above the substrate 102. In this scattering method, the charged display particles 108 will be adsorbed on the top sides of the ribs where are undesired regions to be filled. Controlling an amount of the charged display particles 108 filled in each cell 104 becomes hard because the charged display particles 108 are too light to be precisely controlled. In order to solve this problem, referring to FIG. 1B, a squeegee method has been shown. In this squeegee method, the charged display particles 108 are arranged on the substrate 102 having a plurality of cells 104 and a plate member 112 called a squeegee is moved on the substrate to sweep the charged display particles 108 into the cells 104. However, controlling the amount of the charged display particles 108 filled in each cell 104 is still difficult because the amount of the charged display particles 108 swept into the cells 104 gradually decrease while the plate member 112 is continuously moving. Thus, the resulting EPD device does not have a good enough uniformity of the amount of the charged display particles 108 in each cell 104, which may cause many problems.
Therefore, a method which can fill the charged display particles by an easy process, which can precisely control the amount of the charged display particles filled in each cell to have a good uniformity, is desired.